The present invention relates generally to the arts of fluid sprinkling and weather control spraying. More particularly, the present invention relates to the art of snow making and an improved method and apparatus for artificially making large volumes of high quality snow suitable for skiing.
The present invention pertains to an improvement over my inventions disclosed in U.S. Pat. No. 3,822,825 issued July 9, 1974 and U.S. Pat. No. 3,952,949 issued Apr. 27, 1976. A suitable discussion giving a major portion the prior art background of the present invention is presented in these patents and is accordingly incorporated herein by reference.
Generally, my former inventions for artificially producing snow as disclosed in these two patent references consist of a method and apparatus for making snow through the use of snow towers wherein water is supplied under pressure to a point of discharge well above ground level and adjacent the top end of the tower where it is discharged through a first nozzle into the ambient freezing atmosphere in a form of a spray. The spray is preferably a high velocity spray of discrete water particles, sometimes referred to as a fine water spray.
Air is supplied independently under pressure to a second point of discharge at the top of the snow tower and there discharged through an orifice to form a jet stream which is directed into the throat of the aforesaid water spray thereby forming a plume of atomized or nucleated water. This atomized water forms seed crystals in the freezing atmosphere, and through the dwell time of the long fall from the top of the tower to the ground, forms snow. My prior method and apparatus for making snow provides excellent quality snow in reasonable quantities and at a reasonable cost. However, it is always desirable to make much larger quantities of excellent quality snow over the same period of time with greater efficiency and lower costs.
In addition to my previous inventions pertaining to snow making towers, some other systems for making snow also merit mention for providing a good background understanding of the art.
One of these other snow making systems can generally be described as a moveable fan blower system and basically consists of a water nucleator spray nozzle positioned in front of a rather large fan which drives the air into a nucleated water spray to produce snow. This unit also carries an air compressor with it and the nucleated water spray is produced internally in a mixing chamber wherein the compressed air and water under pressure are mixed and then discharged through a nozzle. Additional water nozzles are circumferentially positioned about the fan which must be regulated from time to time by turning some or all of them on or off in order to balance the quantity of water which may be supplied under pressure to the quantity of air driven by the fan into the sprayed water for the particular ambient freezing temperature conditions then prevalent. Obviously, with my prior art snow towers and also with such a fan blower system, and most systems for that matter, the amount or quantity of water which may be discharged into the atmosphere in order to continue making quality snow varies inversely with the ambient subfreezing temperature.
In other words, at temperatures only slightly below freezing the water supply has to be reduced in order to prevent the production of wet snow, and as the temperature decreases the water supply discharged into the driven air stream may be increased thereby producing larger quantities of good quality snow at lower freezing temperatures. If too much water is supplied for a given ambient temperature, not only will wet snow be produced but too much water will melt the existing snow accumulation. Accordingly, in warmer ambient freezing or subfreezing temperatures, some of the peripheral water jets of the fan blower type apparatus must be shut off and in my snow making tower system as previously described, no adjustments are required until the temperature rises to about 28 degrees F., and the system is then simply shut off. It is not monetarily or effectively practical to operate any snow making apparatus above this temperature.
This temperature limit of approximately 28 degrees F. is actually variable, depending on the humidity or dew point. This maximum temperature would be 24 degrees F. at 90% humidity or only 22 degrees F. at 100 degrees humidity. These are dry bulb temperatures. Actually this maximum temperature is more accurately defined as approximately 22 degrees F. wet bulb or dew point temperature. Above this no system can practically make snow as it is too costly and snow quality can be greatly affected.
These fan blower snow making apparatus are provided as a mobile unit which may be towed about the ski slope by a vehicle. Of course they are relatively heavy units (600 lbs., more or less) in view of the fact that they not only have a heavy housing with cowling protection but are also provided with a heavy 15 HP motor for driving the fan and with a self contained air compressor, all of which provide moving parts which require maintenance, can freeze up and some parts are prone to rusting. This type of fan blower system can meritorously deliver up to a capacity of approximately 125 gal. of water per minute maximum. However, this maximum water supply can only be effectively and actually used to make snow if the ambient temperature is below 10 degrees F. Unfortunately in ski country, this temperature condition normally occurs only about 20% of the time during the winter ski season. Thus during 80% of the snow making weather, the maximum water expulsion possible for making snow is somewhere between 30 to 80 gal. per minute with an average probably somewhere below 50 gal./min. For example, if this system is operated at an ambient temperature of 28 degrees F. it will be limited to a maximum useable water consumption rate which is probably in the area of 35 gal./min.
To generate snow at a water consumption rate of 50 gal./min. with this fan blower system requires a total work effort of about 35 HP per minute, 15 HP for the fan motor, 15 HP for the water supply and 5 HP for the air compressor. This system is also understandably expensive to manufacture and can retail on todays market for up towards $18,000 per unit, depending upon accessories.
The fan used in this prior art ground unit requires a cage enclosure for safety, which is prone to collect ice thereby reducing efficiency. In addition, since the unit is at ground level, the ground surface distribution of snow is narrow as it is limited to the fan capabilities.
In view of the fact that the water nucleation is created in an internal chamber wherein the water under pressure is mixed with the air under pressure before the nucleated spray is discharged, the maximum useable water pressure for nucleation is limited to the air pressure value since a greater water pressure would cause the water to back down the air supply tube.
Another fan blower system of the prior art is generally comprised of a fan wherein water is centrally ejected from a hollow axle at the face of the fan blade. No additional air supply is utilized. The unit weighs in the vicinity of 300 lbs. and is mounted on top of a support which stands about thirty feet maximum off the ground. Higher supports are not practical in view of the unit weight. These units tend to form ice on fan blades and drip water. Ice flying off the blade can also be a safety hazard. Also many of the disadvantages prevalent with the mobile fan blower units are also applicable to these units. They retail in the area of $12,000. In otherwords, they cannot be realistically mounted at the same level as the top of a conventional snow tower which, prior to my present invention, use to be generally in the area of at least 35 feet. This in and of itself is a disadvantage as I have discovered that when a smaller dwell time is provided from the time the seed crystals are formed to the time that the resultant snow touches the ground, lesser quality snow is produced.